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W. H. ELKINS.

REGULATOR FOR DYNAMO ELECTRIC MACHINES.

No. 412,700. Patented Oct. 8, 1889.

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UNITED STATES PATENT OFFICE.

\VILLIAM H. ELKINS, OF CAMBRIDGE, MASSACI'IUSETTS, ASSIGNOR OF TIMO-THIRDS, BY DIRECT AND MESNE ASSIGNMENTS, TO ARTHUR B. GRIGGS, OF BOSTON,MASSACHUSETTS, AND POLLY CRAIG, OF DE FUNIAKSPRINGS,

FLORIDA.

REGULATOR FOR DYNAMO-ELECTRIC MACHINES.

SPECIFICATION forming part of Letters Patent No. 412,700, dated October8, 1889. Application filed January 18, 1889. Serial No. 296-753. (Nomodeh) To all whom it may concern:

Be it known that 1, WILLIAM HENRY Ema ms, of Cambridge, in the county ofMiddlesex and State of Massachusetts, have invented a new and usefulRegulator for Dynamos, of which the following is a specification,reference being had to the accompanying drawing, which is a diagramillustrating my invention, the pole-pieces and cores being shown indotted lines, and the circuit which constitutes the main novelty beingshown in full lines.

Myinvention relates to regulating the current in the work-circuit of adynamo and it consists in a novel compound dynamo-circuit differingmaterially from all other dynamocircuits known to me, as will be nowfully explained.

In the drawing, A represents the armature, and a the commutator, of anordinary dynamo; B, the positive brush, and B the negative brush, and Ban additional brush, The workcircuit is from additional brush B throughlamps L and field F F, to main brush B. The regulating-circuit is frombrush B, through resistance R, to its junction 1) with the workcircuit.

In practical operation the resistance in the work-circuit B L F F B isconstant, excepting as it is varied by varying the load, as byintroducing a different number of lamps L, and in the diagram I haveshown five lamps or groups of lamps, so that the variable load may bedivided into five portions. It will be found that the brush B may be soadjusted in any given dynamo with a given speed that the desired currentwill be maintained over the work-circuit B L F F B when only one lampout of the tivethat is, one-fifth of the Variable loadis used, theregulating-circuit B R bbeing' then open, or, what is practically thesame thing, the resistance R being very large. Under these conditions,if a second lamp, or anotherlifth of the load, beintroduced into thework-circuit B L F F B, the current in the work-circuit will bedecreased, for the speed of the dynamo and electro-motive force remainthe same; but the resistance or load L is doubled, and consequently thetwo lamps L, or two-fifths of the total number of lamps,

will not be at full candle-power. To remedy this the electro-motiveforce of the work-circuit B L F F B must be increased. An ammeter in theworlccireuit B LF F B will indicate when the current in the work-circuitis thus decreased by the introduction of another fifth of the load, andthe regulating-circuitB R Z) will then be closed through resistance R,thus establishing a regulating-current through the circuit B R Z) L F FB, this additional current bringing up the current in the work circuitto the proper standard. \Vhen a third fifth of the load L is introduced,the current in the work-circuit again decreases, and is again brought tostandard by aid of the regulating-circuit by still further decreasin gthe resistance R, and so on until the whole load is in the work-circuit,when the resistance R is eliminated, or practically so, the work-circuitbeing then from brush B to brush B practically as if the brush B and there- 7c then open, or practically so, and that as the resistance R-in theregulating-circuit is decreased the difiference in potential between Band Z) diminishes, there being but slight difference in potentialbetweenB and b with about four-fifths of the load in the work-circuit, whilewith full load in the work-circuit and the resistance R decreased topractically nothing there will be a current from Z) to B instead of acurrent from B to b, as is the case when three-fifths or less of thefull load is in the work-circuit. In theory under the minimum load-sayone-fifth of the full load there should be no current in theregulatingcireuit for the best results, and the additional brush Bshould be set to give the desired current in the worlecircuit when theload is at the minimum, and then be drawn toward the brush B after, say,about one-half of the full load is introduced into the work-circuit, inorder to prevent any possibility of a current from b to 13 but, as willbe clear, a second additional brush might be used between B and B, wherea closer degree of regulationsay from sixty lamps to only one or two-wasrequired; or brush B may be moved toward B as indicated by dotted line BIn practice I have succeeded in maintaining acon stant current in thework-circuit, although the load varied from one-fifth to fourfifths, thecurrent from B to I) being with one-fifth load, and with theregulating-circuit open, the same, of course, as in the workcircuit; butwith two-fifths load in the workcircuit the current from B to 1)decreased and the current from B through R to I) increased, and soon,until with four-fifths load there was no current from B to b, and thecurrent from Bthrough R to b was the same as that in the work-circuit;but, as before observed, in this case under full load the current from Bthrough R (B being then reduced to practically nothing) to Z) wasgreater than the current in the main circuit, and the excess flowed fromb to B and back through the coils of the armature to B. This backflow ofa portion of the current is not desirable, and can readily be preventedby moving the brush B nearer to the brush B, or by the use of brush B,as indicated by B It will be clear to all skilled in the art how theresistance B may be adjusted, and therefore no means are described orshown in the drawing.

What I claim as my invention is- In combination with the armature A andits commutator a, themain brushes B B',the additional brush B and theadjustable resistance R, the brushes B and B being connected to thework-circuit at b, with the resistance R between the brush B and thejunction 17, all arranged and operating as described to keep the currentconstant by variations in the current supplied by the brushes B and B,substantially as described.

. WILLIAM H. ELKINS,

WVitnesses:

EDWARD S. BEACH, J OHN R. Snow.

